Field
The present invention relates to methods for controlling and/or regulating a compressed-gas-operable medical or dental drive device and such a drive device.
Description of Prior Art
Known methods for controlling and/or regulating a compressed-gas-operable medical, in particular dental, drive device are diagrammed schematically in FIGS. 1 and 2 on the basis of torque/rotational speed diagrams. The two figures each show a torque/rotational speed diagram of a drive device that can be induced to rotate, in particular of a rotor that can be acted upon by compressed gas and/or a tool-holding device connected thereto. The rotational speed (n) of the drive device is plotted on the abscissa and the torque (M) is plotted on the ordinate. In addition, the diagrams show as examples a few pressure curves (straight lines p1, p2, pmax), each representing a gas pressure value of the compressed gas. The pressure value pmax is the highest available pressure gas value, wherein the drive device usually has a valve that limits the gas pressure to the maximum value pmax. A rotational speed n1, n2, nmax correlates with each gas pressure value p1, p2, pmax, where nmax stands for the highest achievable rotational speed.
It should be pointed out that the diagrams in FIGS. 1 and 2 as well as all additional diagrams are considered fundamentally in the direction of increasing torque. The description is also worded accordingly. However, the invention is of course not limited to this approach, but instead clearly also includes a characteristic in the direction of decreasing torque, as also shown in the diagrams.
FIG. 1 shows a torque/rotational speed diagram of a known method for controlling a compressed-gas-operable medical or dental drive device. This drive device has a control valve, which can be operated by a user through an adjusting device that can be operated by foot (referred to below as a foot control) and is designed to control the gas pressure and/or the flow rate of the compressed gas according to the foot control position and thus to determine the rotational speed of the rotor. If the user selects the pressure value p1 as the desired pressure in idling, for example, by operating the foot control and thus operating the control valve, then the rotor will rotate at the rotational speed n1, and the situation is similar for each additional selectable pressure and the respective rotational speed see, for example, the pressure value p2 and the rotational speed n2 as well as the maximum pressure value pmax and the maximum rotational speed nmax. Correspondingly, the torque of the drive device or the torque of the rotor is at least almost zero in idling accordingly. “In idling” means that a tool held in the tool-holding device does not come in contact with a part that is to be worked, in particular a body tissue such as a tooth, a bone or a replacement material, and therefore the tool is not applied by a load.
If the user contacts a part that is to be processed with the tool or if the user applies a load to the tool, then, depending on the magnitude of the load, the rotational speed declines according to the course of the straight lines assigned to the respective pressure value p1, p2, pmax and the torque increases accordingly. The torque reaches its maximum value when the rotational speed is zero.
Work on a body tissue thus comprises a permanent direct or indirect change in rotational speed, torque and gas pressure by the user, for example, by means of the foot control, exclusively on the basis of the user's perception, for example, the visually observed removal of material or the speed of rotation of the tool, the force to be applied by hand to the part to be processed or the frequency of the drive device. Therefore the user can achieve the various settings for the rotational speed, the torque and/or the gas pressure desired for different treatments, for example, only approximately on the basis of his senses.
FIG. 2 shows a torque/rotational speed diagram of a second known method for regulating the rotational speed of a compressed-gas-operable medical or dental drive device. The method of FIG. 2 corresponds to the method of FIG. 1, but regulation is provided when the rotor reaches a predetermined rotational speed value n3. The rotational speed value n3 defines a rotational speed limit value which is not exceeded and/or at which is regulated by regulating the supply of compressed gas by means of a control valve. When the user increases the gas pressure or flow rate of the compressed gas, the torque of the rotor or the torque of the tool thereby driven is increased, optionally until reaching the maximum gas pressure pmax. The torque increases further if the load on the tool increases further but the rotational speed then declines accordingly (see the rotational speed/torque characteristic line emphasized in FIG. 2). Such a method is known from the patent application US 2008/0145817 A1, for example. Thus, during operation a defined course for a rotational speed value (n3) or a predetermined ratio of rotational speed, torque and gas pressure is available to the user, but for all rotational speeds below this predetermined rotational speed value (n3), the user must again rely on his senses, as described above with regard to FIG. 1.